What is the good of a plastic bag ban that doesn’t really ban plastic bags?

Honolulu taxpayers might well be pondering that very issue. And they ought to be asking the Honolulu City Council whether the new ordinance will accomplish its goal — to reduce the amount of plastic in the environment — when it takes effect July 1.

It may become clearer in the coming months how the ban on single-use shopping bags will play out, once the city Department of Environmental Services gets some feedback from retailers about how they plan to implement the ordinance. Of course, some retailers and their advocates, who have opposed the ordinance since it passed in 2012, may continue to press for changes, complicating matters further.

But based on experiences in Hawaii’s other counties, it appears likely that many shops here would simply substitute a tote that’s allowed under the ordinance: a thicker plastic bag that’s suitable for reuse.

And unless there are changes to the law to incentivize a bring-your-own ethic among customers, Oahu could be simply substituting one type of bag for another.

The original ordinance was amended in 2014 to eliminate "biodegradable" bags from the allowed list and require instead that the substitutes be certifiable as "compostable."

The amendment left intact the exemption for plastic bags measuring at least 2.25 mils in thickness (a "mil" being a thousandth of an inch). Retailers are not required to charge a fee for these bags, which means customers won’t feel driven to change their habits.

And changing habits should be what a plastic-bag ban is all about. Retailers will keep ordering plastic bags as part of the cost of doing business, folding it into the cost of the merchandise and passing it on. The only advantages may be that the heavier bags are less prone to flying off on a breeze and ending up as ocean trash, and to the extent that they’re more durable, each may be able to carry more.

Still, these are weak improvements, especially considering the more than three-year gap between the passage of the ordinance and its effective date.

Some businesses are already experimenting with their own incentives. At Foodland, for example, customers who did not require a store-supplied bag were rebated a nickel per bag of groceries. That’s a good way to win some customer favor, but voluntary incentives offered by the retailer may not be enough of an inducement.

In the next month, the city plans to issue written notices to some 15,000 retailers to remind them of the July 1 deadline and query them on how they plan to comply.

Once those responses are in hand, it would be a good time for the Council to take a last look at the ordinance and again consider what should have been done in the first place: requiring a small fee per plastic bag issued at the point of sale.

Otherwise, the cost of bags will be passed on in the price of groceries, which is unfair to customers who take responsibility and bring their own totes with them.

There’s a good reason why so many municipalities across the country have moved to cut the use of single-use shopping bags. The same features that make the bags so popular — their light weight and their resistance to breakdown — means they also escape easily into the environment and persist there for a long time. In the ocean, stray plastic bags can harm a lot of marine life.

Moreover, using fewer disposable paper and plastic bags will reduce the energy costs associated with manufacturing them.

Few would dispute these facts. Now what is needed is a city policy that recognizes them, by encouraging conservation where it’s possible. A stronger push to reduce plastic in the environment would be a good starting point.